Method and Apparatus for Scheduling Request

ABSTRACT

The present invention provides a method of performing Scheduling Request (SR) in a user equipment (UE) of a wireless communication system. The method includes steps of triggering an SR, sending an SR message on a Physical Uplink Control Channel (PUCCH) when the UE has a configured PUCCH resource, and skipping a plurality of subsequent SR transmission opportunities after the SR message is sent.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/228148, filed on Jul. 23, 2009 and entitled “Advanced Transmissionand Reception for DRX and SR”, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for performingScheduling Request, and more particularly, to a method and apparatus forperforming Scheduling Request in a user equipment (UE) of a wirelesscommunication system to reduce unnecessary Scheduling Requesttransmission when the Scheduling Request is sent in a short periodicity,such that power consumption can be saved.

2. Description of the Prior Art

Long Term Evolution wireless communication system (LTE system), anadvanced high-speed wireless communication system established upon the3G mobile telecommunication system, supports only packet-switchedtransmission, and tends to implement both Medium Access Control (MAC)layer and Radio Link Control (RLC) layer in one single communicationsite, such as in base stations (Node Bs) alone rather than in Node Bsand RNC (Radio Network Controller) respectively, so that the systemstructure becomes simple.

In LTE system, the network, such as an evolved Node B (eNB), performsradio resource allocation to provide user equipments (UEs) withresources for uplink or downlink data transfer. There are two kinds ofresource allocations: dynamic resource allocation and pre-configuredresource allocation. For the pre-configured resource allocation, thenetwork allocates resource to the UEs by Radio Resource Control (RRC)signaling, and allows the UEs periodically transmitting a certain amountof data, for example, voice data. That means, at periodic timeintervals, the UEs can utilize the pre-configured radio resources fordata transmission or reception, to achieve data exchange with thenetwork. On the other hand, for the dynamic resource allocation, thenetwork dynamically allocates radio resources to the UEs depending on UEnumber of the cell area, traffic volume and quality of service (QoS)requirements of each UE, and the UE has to monitor a physical downlinkcontrol channel (PDCCH) to find possible allocation of dynamic resourcesfor both downlink and uplink transmission.

For the dynamic resource allocation, when the UE has new uplink data totransmit and there is no Uplink Shared Channel (UL-SCH) resourceavailable, the UE shall trigger a Scheduling Request (SR) procedure torequest the network to allocate uplink transmission resources. In such asituation, if the UE has configured Physical Uplink Control Channel(PUCCH) resources, the SR procedure is performed via PUCCH signaling.Otherwise, such as the UE has no configured PUCCH resources or theconfigured PUCCH resources are invalid, for example, the SR procedure isthen performed via a Random Access Procedure. Since the PUCCH resourcesare dedicated transmission resources, the SR message transmitted onPUCCH is referred to as a Dedicated Scheduling Request (D-SR) message,while the SR message transmitted via the Random Access procedure isreferred to as a Random Access Scheduling Request (RA-SR) message.

If the UE has a configured PUCCH resource after an SR is triggered, theUE shall periodically transmit a D-SR message on PUCCH until the SR iscancelled. Note that the SR is cancelled when an uplink transmissionresource for a new transmission is received or the number of D-SRtransmissions reaches to a pre-defined parameter DSR_TRANS_MAX. When thenumber of D-SR transmissions reaches to the pre-defined parameterDSR_TRANS_MAX, it indicates uplink transmission of the UE may have someproblem, such as the PUCCH resources for SR become invalid (probably dueto poor signal quality or improper power settings) or the UE losessynchronization on uplink timing, and thus the D-SR messages sent by theUE cannot be successfully received by the network. In this case, the UEshall stop the D-SR transmission, and trigger a Random Access procedureto transmit the SR message instead.

According to current specifications, a minimum periodicity for sendingSR on PUCCH is 5 ms. It means that UE can send an SR on PUCCH every 5ms. In this case, the average waiting time required by the UE forsending SR on PUCCH is 2.5 ms. For the growing demands on real-timecommunication services, the waiting time may be too long. Thus, it hasbeen proposed by the industry to consider having a shorter periodicitylike 2 or 3 ms. However, when the periodicity is shorter than the timeexpenditure the eNB requires to handle the SR message or shorter thanpacket Round Trip Time (RTT), some of the SR transmission is redundant,and causes unnecessary power waste of the UE.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide amethod and apparatus for performing Scheduling Request (SR) in a userequipment (UE) of a wireless communications system.

According to the present invention, a method for performing SchedulingRequest (SR) in a user equipment (UE) of a wireless communication systemis disclosed. The method includes steps of triggering an SR; sending anSR message on a Physical Uplink Control Channel (PUCCH) when the UE hasa configured PUCCH resource; and skipping a plurality of transmissionopportunities for sending the SR message after the SR message is sent.

According to the present invention, a communications device forperforming Scheduling Request (SR) in a user equipment (UE) of awireless communication system is disclosed. The communications deviceincludes a processor for executing a program code, and a memory, coupledto the processor, for storing the program code. The program codeincludes steps of triggering an SR; sending an SR message on a PhysicalUplink Control Channel (PUCCH) when the UE has a configured PUCCHresource; and skipping a plurality of transmission opportunities forsending the SR message after the SR message is sent.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communications system.

FIG. 2 is a function block diagram of a wireless communications device.

FIG. 3 is a diagram of a program code of FIG. 2.

FIG. 4 is a flowchart of a process according to an embodiment of thepresent invention.

FIG. 5 is an operational diagram of the process of FIG. 4 according tothe embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which illustrates a schematic diagram of awireless communications system 10. The wireless communications system 10is preferred to be a Long Term Evolution (LTE) system, and is brieflycomposed of a network and a plurality of user equipments (UEs). In FIG.1, the network and the UEs are simply utilized for illustrating thestructure of the wireless communications system 10. Practically, thenetwork may comprise a plurality of base stations (Node Bs), radionetwork controllers and so on according to actual demands, and the UEscan be devices such as mobile phones, computer systems, etc.

Please refer to FIG. 2, which is a functional block diagram of acommunications device 100 in a wireless communications system. Thecommunications device 100 can be utilized for realizing the UEs in FIG.1, and the wireless communications system is preferably the LTE system.For the sake of brevity, FIG. 2 only shows an input device 102, anoutput device 104, a control circuit 106, a central processing unit(CPU) 108, a memory 110, a program 112, and a transceiver 114 of thecommunications device 100. In the communications device 100, the controlcircuit 106 executes the program 112 in the memory 110 through the CPU108, thereby controlling an operation of the communications device 100.The communications device 100 can receive signals input by a userthrough the input device 102, such as a keyboard, and can output imagesand sounds through the output device 104, such as a monitor or speakers.The transceiver 114 is used to receive and transmit wireless signals,delivering received signals to the control circuit 106, and outputtingsignals generated by the control circuit 106 wirelessly. From aperspective of a communications protocol framework, the transceiver 114can be seen as a portion of Layer 1, and the control circuit 106 can beutilized to realize functions of Layer 2 and Layer 3.

Please continue to refer to FIG. 3. FIG. 3 is a schematic diagram of theprogram 112 shown in FIG. 2. The program 112 includes an applicationlayer 200, a Layer 3 202, and a Layer 2 206, and is coupled to a Layer 1218. The Layer 3 202 is used for performing resource control. The Layer2 includes a Radio Link Control (RLC) layer and a Medium Access Control(MAC) layer, and is used for performing link control. The Layer 1 218 isused for performing physical connection.

In LTE system, when the UE has new uplink data to transmit such asuplink data arrives to a transmission buffer of the UE, for example, andthere is no Uplink Shared Channel (UL-SCH) resource available, the UEwould trigger a Scheduling Request (SR) procedure to request the networkto allocate uplink transmission resources, such that the uplink data canbe transmitted. Under such a situation, the embodiment of the presentinvention provides a scheduling request program 220 in the program 112for avoiding unnecessary transmission of scheduling request messages andsaving UE power consumption.

Please refer to FIG. 4, which illustrates a schematic diagram of aprocess 40 according to an embodiment of the present invention. Theprocess 40 is utilized for performing Scheduling Request (SR) in a UE ofa wireless communication system, and can be compiled into the schedulingrequest program 220. The process 40 includes the following steps:

Step 400: Start.

Step 402: Trigger an SR.

Step 404: Send an SR message on a Physical Uplink Control Channel(PUCCH) when the UE has a configured PUCCH resource.

Step 406: Skip a plurality of SR transmission opportunities after the SRmessage is sent.

Step 408: End.

According to the process 40, after the SR is triggered, if the UE hasconfigured PUCCH resources, the UE sends an SR message on PUCCH. Afterthe SR message is sent, the UE then skips a plurality of transmissionopportunities for sending the SR message. In this case, even a short SRperiodicity is used by the UE to transmit the SR message, since theplurality of SR transmission opportunities is skipped each time afterthe SR message is sent, the embodiment of the present invention is ableto reduce unnecessary transmission of the SR message, while the averagewaiting time for sending the SR message can still be shortened.

If the SR is still pending (i.e. not being cancelled) after theplurality of transmission opportunities is skipped, the UE shall keep onsending the SR message at a next transmission opportunity. Note that theSR is cancelled when an uplink transmission resource for a newtransmission is received or the number of times the SR message is sentreaches to a pre-defined parameter DSR_TRANS_MAX.

For example, please refer to FIG. 5. FIG. 5 is an operational diagram ofthe process 40 according to the embodiment of the present invention.Assume that an SR is triggered due to uplink data arrival at a timingpoint T1. If the UE has configured PUCCH resources, transmissionopportunities for the UE to send an SR message would be periodicallyformed on PUCCH (timing points T2-T6). The time interval between eachtransmission opportunity is configured according to periodicity of thePUCCH resource, which can be 1 ms to 4 ms but is not limited to these.In the beginning, the UE sends the SR message at a first transmissionopportunity (i.e. at the timing point T2). Then, based on the process40, the UE skips a plurality of transmission opportunities, such as twotransmission opportunities in this case, for example. If the SR is stillpending after the plurality of transmission opportunities is skipped,the UE then sends the SR message again at a next transmissionopportunity (i.e. at the timing point T5). And, the UE repeats in thismanner until the SR is cancelled.

In the present invention, since the plurality of follow-up transmissionopportunity is skipped by the UE each time after the SR message is sent,the UE is able to avoid unnecessary transmissions of the SR message tillreceiving response from the network, so that the power consumption canbe saved. Accordingly, the short SR periodicity can still be used by theUE, and thus the average waiting time required by the UE for sending theSR message (i.e. the time interval between the timing points T1 and T2)can be significantly shortened as well.

It is worth noting that appropriate modifications or alternations can becertainly made by those skilled in the art according to practicaldemands, which all belong to the scope of the present invention. Forexample, the way that the UE skips the plurality of opportunity can becontrolled by a counter or a timer, which is also not restricted bythis.

As mentioned above, the embodiment of the present invention provides amethod and apparatus for performing scheduling request to avoidunnecessary transmission of the SR message when the UE uses the short SRperiodicity, such that power consumption can be saved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method for performing Scheduling Request (SR) in a user equipment(UE) of a wireless communication system, the method comprising:triggering an SR; sending an SR message on a Physical Uplink ControlChannel (PUCCH) when the UE has a configured PUCCH resource; andskipping a plurality of transmission opportunities for sending the SRmessage after the SR message is sent.
 2. The method of claim 1, whereinthe SR is triggered when uplink data arrives to a transmission buffer ofthe UE and there is no uplink transmission resource available.
 3. Themethod of claim 1 further comprising: keeping on sending the SR messageat a next transmission opportunity next to the plurality of transmissionopportunities when the SR is still not cancelled.
 4. The method of claim3, wherein the SR is cancelled when the UE receives an uplinktransmission resource allocated to a new transmission.
 5. The method ofclaim 4, wherein the uplink transmission resource is an Uplink SharedChannel (UL-SCH) resource.
 6. The method of claim 3, wherein the SR iscancelled when the number of times that the SR message is sent reachesto a pre-defined number.
 7. The method of claim 1, wherein the number ofthe plurality of transmission opportunities is determined by a timer. 8.The method of claim 1, wherein the number of the plurality oftransmission opportunities is determined by a counter.
 9. Acommunication device for performing Scheduling Request (SR) in a userequipment (UE) of a wireless communication system, the communicationdevice comprising: a processor for executing a program code; and amemory coupled to the processor for storing the program code; whereinthe program code comprises: triggering an SR; sending an SR message on aPhysical Uplink Control Channel (PUCCH) when the UE has a configuredPUCCH resource; and skipping a plurality of transmission opportunitiesfor sending the SR message after the SR message is sent.
 10. Thecommunication device of claim 9, wherein the SR is triggered when uplinkdata arrives to a transmission buffer of the UE and there is no uplinktransmission resource available.
 11. The communication device of claim9, wherein the program code further comprises: keeping on sending the SRmessage at a transmission opportunity next to the plurality oftransmission opportunities when the SR is still not cancelled.
 12. Thecommunication device of claim 11, wherein the SR is cancelled when theUE receives an uplink transmission resource allocated to a newtransmission.
 13. The communication device of claim 12, wherein theuplink transmission resource is an Uplink Shared Channel (UL-SCH)resource.
 14. The communication device of claim 11, wherein the SR iscancelled when the number of times that the SR message is sent reachesto a pre-defined number.
 15. The communication device of claim 9,wherein the number of the plurality of transmission opportunities isdetermined by a timer.
 16. The communication device of claim 9, whereinthe number of the plurality of transmission opportunities is determinedby a counter.